For all practical purposes they have that now. The CD on tesla cars is very low, and even AP1 cars will follow other vehicles on the highway for hundreds of miles without a hitch.
The AP follow distance setting can be set from 1 to 7, and setting it to 1 just ends up with more abrupt braking when traffic encounters a slowdown. A spaced out setting of 4 is a much more comfortable setting.
If the cars were able to push and pull each other, engines/batteries could be used optimally. Cars with nearly empty batteries would recuperate and recharge if absolutely needed, cars with full batteries would pull the rest. AP would put the most suitable car in front to minimize the total air resistance... Lots of possibilities.
Might be worth designing a new type of car for this kind of use though.
The AP follow distance setting can be set from 1 to 7, and setting it to 1 just ends up with more abrupt braking when traffic encounters a slowdown. A spaced out setting of 4 is a much more comfortable setting.